ABSTRACT
To decide whether people become less or more variable as they grow older, experimental psychologists must define the timescales and contexts in which they study them. Authors such as K. M. Newell suggest that increases in the kind of variability with age represent increases in the random noise in the neurological systems that control movements. This may be so, but muscle tremor and variability in grip and contraction speed cannot explain the entire variability of reaction times in easy continuous tasks because we can separately measure the movement components and the decision components of responses. Brian Stollery’s remarkable charm and empathy persuaded 90 Manchester residents to volunteer for one of the longest, most tedious psychological studies ever made. Excellent studies at the University of British Columbia confirm that moment-to-moment variability increases with age and with poor health, brain damage and the onset of Alzheimer’s dementia.
